What are the last three digits on your computer? That way I can look at the schematic and find the fuse as well as the led driver. It should also enable me to find the proper connections and values on the connector. To replace either one requires board level soldering.

5 Answers

Looks like your client shorted the LVDS connector. If you're lucky the connector is ok but the backlight fuse is blown. Use a multimeter to check the fuse resistance or continuity. It's a small 0402 or 0603 IC on the logic board. The IC has a P or a F or a white dote on it.

Nathan Reeves, here is a copy of my answer to a very similar question "besides a bad connector on the logic board, like Nathan Barnes suggest, there is still the possibility of a bad inverter circuitry (the LED driver), a bad backlight fuse, as well as a multiple others:-). Here is what Apple suggest to do first :-)

5. Reset PRAM. If no action, use external keyboard with same sequence. Verify that system video is displayed.

Yes Invalid or corrupt PRAM contents affecting video output.

No Go to step 6.

6. Connect external video:

Connect known-good VGA/DVI adapter to known-good display, press power button and close display to force main screen startup on external video. Verify that video is correct when displayed from external display.

Yes Video correct on external display. Research available firmware and software updates, retest. If returning with software already updated, go to step 7.

No Replace logic board with according symptom code:

-no video

-bad/distorted video

7. Isolate LCD display detection:

Disconnect external monitor and reopen display and restart unit. Verify that sleep LED indicator goes off after internal LCD has been detected.

Yes Sleep LED goes off when LCD detected.

-If still no video then Go to step 8,

-If video present, but with defect, go to step 9.

No Internal LCD not detected.Run Clamshell Service Diagnostic utility and check for LCD panel presence. If not found, reseat LVDS cable connection on logic board and retest. If sleep LED does not go off after cable is reseated, go to step 10.

8. Check for sleep sensor condition. If display assembly sleep sensor is stuck in a closed state, video will appear on internal display temporarily, until the OS sleeps the system. Disconnect BIL/ sleep cable and restart unit without external display. Verify that system starts up with video on internal display stays on and does not go into sleep mode.

- if cable is not damaged, run Clamshell Service Diagnostic utility and check for LCD

panel presence. If not found, reseat cable and retest, then go to step 11.

No If symptom continues, go to step 10.

10. Verify with Known good display assembly Connect known-good display assembly to system.

Yes System is functioning with known-good display assembly. Replace display assembly if following symptom reporting:

- had no power issue

- had incorrect/missing colors

- had blank video

- had distorted / blurred video

- had vertical/horizontal lines

- had noise/unstable flickering

- had dim backlight

- had bad spot(s)/pixels

- had no backlight

- could not change resolution

No Symptoms unchanged - replace logic board.

11. Verify with reseated LVDS cable or replaced display assembly Verify that unit now has video and backlight.

Yes Issue was only due to damaged display assembly or unseated cable.

No Display cable damaged the logic board. Replace logic board."

Here is the pinout for the LVDS connector, and there are only a few that you can check with a multimeter:"

1 GND Ground

2 Vcc Power Supply (+3.3V)

3 Vanalog Power Supply (+3.3V)

4 VEDID DDC Power +3.3V

5 Vsync Vsync

6 ClkEDID DDC Clock

7 DATAEDID DDC Data

8 Rin0- Differential Data Input

9 Rin0+ Differential Data Input

10 GND Ground

11 Rin1- Differential Data Input

12 Rin1+ Differential Data Input

13 GND Ground

14 Rin2- Differential Data Input

15 Rin2+ Differential Data Input

16 GND Ground

17 Clkin- Differential Clock Input

18 Clkin+ Differential Clock Input

19 GND Ground

20 NC NC

21 Vdc(1 &2) LED Annold (Positive)

22 Vdc(3&4) LED Annold (Positive)

23 NC NC

24 Vdc1 LED Cathode (Negative)

25 Vdc2 LED Cathode (Negative)

26 Vdc3 LED Cathode (Negative)

27 Vdc4 LED Cathode (Negative)

28 Vdc5 LED Cathode (Negative)

29 Vdc6 LED Cathode (Negative)

30 NC NC

Of course you also want to check the backlight fuse It is a 3amp - 32V 467 packaging fuse. Check with an ohmmeter for continuity. Last but not least, it could be the LED driver LP8543SQX/NOPB-ND Datasheet is available right here. If you can attach top and bottom view images of your logic board. We can probably show you where those components are located. I am not a Mac person, and I am sure the real gurus can figure it out better than I can. Hope this helps, good luck.

OK I had this exact same problem (and I am a hardware tech, fyi). It occurred when the displayport jack was inserted crooked - the entire machine shutoff and then only external display worked.

I tried everything - Apple Service Diagnostics didn't help, neither did clearing PRAM or SMC. Then I obtained schematics for the Macbook (this is a 2009 2.53Ghz Core 2 15") and replaced the MOSFETS and power switch that the Displayport uses. Still no dice.

Finally, I booted it with the internal display unplugged. Then power cycled with the display plugged in and...it works! *scratches head* - these computers are a mystery to me at all times. It must have reset some crazy SMC MUX detect or something(?) I honestly have no idea. But worth a try.

I don't have an answer, but instead have a similar problem. This page was very helpful but am uncertain how to interpret for the computer in front of me.

It's a 2009 MacBook Pro - I bought it with a busted screen, and since I had another display lying around I thought that would be a quick and easy thing to swap the displays. Unfortunately it wasn't to be that easy.

This computer displays perfectly on an external display. It recognizes there is a second display (the laptop screen) and I can drag windows over to that screen, and it behaves like it's dragging the window to another display, etc. In other words, this laptop believes it has a functioning laptop screen but nothing is shown.

I tried booting with the display cord disconnected. While booted that way it did not show the second display as a possibility. Then rebooting, and the problem did not magically fix itself.

I just tried shining a light on the screen and did not see any faint images. This was done with Display Mirroring on, so to have a known image on the screen. The blackness was uniform across the display.

I've tried swapping in two different displays, both of which "should" be working correctly, with no luck.